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Facebook joins Google in warning DNSChanger victims

Warnings follow decision to withdraw safety net on 9 July

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Federal authorities will not seek a further extension to a DNSChanger safety net, meaning an estimated 360,00 security laggards will be unable to use the internet normally unless they clean up their systems before a 9 July deadline.

DNSChanger changed the domain name system (DNS) settings of compromised machines to point surfers to rogue servers – which hijacked web searches and redirected victims to dodgy websites as part of a long-running click-fraud and scareware distribution racket. The FBI dismantled the botnet's command-and-control infrastructure back in November, as part of Operation GhostClick.

In place of the rogue servers, a bank of duplicate machines was set up to resolve internet look-up queries from compromised boxes. This system was established under a court order, which has already been extended twice. The move meant users of compromised machines could use the internet normally – but the safety net by itself did nothing to change the fact that infected machines needed to be cleaned.

At its peak as many four million computers were infected by DNSChanger. An estimated 360,000 machines are still infected and there's no sign that further extending the safety net will do any good, hence a decision to try other tactics while withdrawing the DNS safety net, which has served its purpose of granting businesses with infected machines time to clean up their act.

Last week Facebook joined Google and ISPs in notifying DNSChanger victims‎ that they were surfing the net using a compromised machine.

"The warnings are delivered using a 'DNS Firewall' technology called RPZ (for Response Policy Zones)," Paul Vixie, chairman and founder of Internet Systems Consortium, told El Reg. "This allows infected users (who are using the 'replacement' DNS servers) to hear different responses than uninfected users (who are using 'real' DNS servers). We can control how an infected user reaches certain websites by inserting rules into the RPZ," he added.

More information – along with clean-up advice – can be found on the DNS Changer Working Group website here. ®